1. Field of the Invention
This invention relates to a bicycle equipped with a drive assist, and particularly to a bicycle equipped with a drive assist in which a drive assist is attached to a novel bicycle in which a trajectory of motion of a pedal lever becomes almost reciprocating motion by using a rotation transmission mechanism having a swing fulcrum, a pedaling force sensor for determining an assist timing of a drive assist is attached to the pedal lever and in which the output from the pedaling force sensor is introduced into a controller through a wire, thereby arranging a pedaling force sensor of a high accuracy and a high response which need not be adjusted.
2. Description of the Related Art
Heretofore, there has been developed a bicycle equipped with a drive assist, i.e. what might be called a motor assist bicycle. This motor assist bicycle has a drive assist with a battery-operating motor attached to a front or rear wheel in order to decrease a load on a user (bicyclist) who rides on a bicycle by operating the drive assist to reduce a pedaling force when a cyclist rides a bicycle in the steep hill where a load is imposed upon the user.
Since assist can be given to a user by a drive assist within a range allowed by regulations, necessity of assist is determined by detecting a pedaling force applied to a pedal lever, and assist is given to a user when a detected pedaling force exceeds a reference value. When such assist timing is determined, a pedaling force should be detected by any means. The user""s pedaling force is measured with the highest accuracy by the pedal lever. To this end, a known pedaling force sensor is attached to the pedal lever so that, when an output from this pedaling force sensor exceeds a reference value, it is determined that assist done by the drive assist is necessary.
When the pedaling force sensor is attached to the pedal lever to measure the pedaling force applied to the pedal lever, the pedal lever is rotated as is conventional so that an output from the pedaling force sensor can not be transmitted through a signal wire (cable) because the signal wire will disturb the rotation motion of the pedal.
For this reason, heretofore, the output from the pedaling force sensor is transmitted to the outside by a suitable means such as a slip ring. However, since a rotary transformer mechanism such as a slip ring is used to transmit the output from the pedaling force sensor to the outside, there arises the problem that the pedaling force detection means will become expensive unavoidably.
There is known an arrangement using not the rotary transformer mechanism but a transmission mechanism such as a cam to transmit the output from the pedaling force sensor to the outside. However, also in this case, since the arrangement comprising a mechanical transducer system such as a number of cams is used, transmission accuracy is not sufficient, and a response speed also is not sufficient. Moreover, since there occurs a transmission loss and there are required increased assemblies, a mutual adjustment becomes necessary, and there arises a problem of maintenance.
It is an object of the present invention to provide a bicycle equipped with a drive assist in which the aforementioned problems can be solved.
According to the present invention, particularly, a drive assist is attached to a novel bicycle in which a trajectory of motion of a pedal lever can be made substantially a reciprocating motion by a rotation transmission mechanism having a swing fulcrum. Also, a pedaling force sensor for determining an assist timing of the drive assist is attached to the pedal lever and an output from the pedaling force sensor is transmitted to a controller through a cable, thereby arranging a pedaling force detection means of high accuracy and high response which can be made free from adjustment.
According to an aspect of the present invention, there is provided a bicycle equipped with a drive assist. This bicycle equipped with a drive assist is comprised of a drive assist attached to a driving wheel, a sprocket provided near a bottom bracket point of a frame comprising a bicycle body, a driving power transmission means attached between the sprocket and a rear wheel, a pair of pedal lever having a phase difference of 180xc2x0, a crank lever provided between said sprocket and one of the pedal levers to transmit a rotation force to the sprocket and a sliding portion serving as a swing fulcrum of the pedal lever, wherein a slide pin provided on one end of the pedal lever slides within the sliding portion in accordance with the rotation of the pedal lever to transmit a rotation force generated in accordance with the rotation of the pedal lever to the rear wheel through the sprocket, a pedaling force sensor attached to a part of the pedal lever which reciprocates approximately, an output from the pedaling force sensor is supplied through a signal line to a controller which controls the drive assist and the bicycle controls an assist timing at which the drive assist is used as a pedal drive assist means based on the output from the pedaling force sensor.
According to the present invention, a rotation force (pedaling force) of the pedal lever is transmitted through the crank lever to the sprocket and there is provided the swing fulcrum to swing the pedal lever. Thus, a bicycle is arranged such that the pedal lever executes substantially a reciprocating motion. That is, the trajectory of the motion of the pedal lever is changed from the rotation motion to the reciprocating motion.
Since the trajectory of the motion of the pedal lever becomes substantially the reciprocating motion, when the pedaling force to the pedal lever is detected by the pedaling force sensor attached to the pedal lever, the output from the pedaling force sensor maybe transmitted through the signal line (cable) to the controller for the drive assist. That is, the output from the pedaling force sensor can be transmitted to the controller by means of the simple cable. Thus, since the pedaling force can be detected with a high accuracy and a high reliability, it is possible to detect the assist timing accurately.